Police have released a photo of the man and woman whose bodies were found in a Branston home earlier this week.
Victims Romanian doctor Premm Monti, 51, and American pensioner Robert Tully, 71 are believed to be the mother of a 22-year-old man, who appeared in court charged with the murders, and her partner.
Simino-Munteanu has been charged with the murders between July 27 and July 30 this year.
The bodies were found on Monday, August 5.
Formal identification has not yet taken place. This is believed to have been an isolated incident, police said.
A plea and trial preparation hearing is due for September 9 and a provisional trial date has been set for February 3, 2020.